A rim cushion is provided on the outer surface of a bead portion of a pneumatic tire in a manner that the rim cushion is in close contact with a rim when the tire is mounted on a rim of a wheel.
Furthermore, for the finishing of a pneumatic tire, a rubber sheet that does not use fibers (so-called rubber finishing) has been used to reduce the weight and/or the cost of the tire.
For example, Patent Document 1 discloses “a rubber composition for tire rim cushion or rubber finishing comprising: from 1 to 30 parts by mass of a polyrotaxane compound having a cyclic molecule with blocked isocyanate group, a straight chain molecule that skewers the cyclic molecule, and terminal groups disposed at both ends of the straight chain molecule preventing the cyclic molecule from being detached from the straight chain molecule, and from 70 to 90 parts by mass of a carbon black whose nitrogen adsorption specific surface area (N2SA) is from 90 to 130 m2/g, per 100 parts by mass of a rubber component comprising from 40 to 60 parts by mass of a natural rubber and from 60 to 40 parts by mass of a diene rubber having a modified group capable of reacting with an isocyanate group” ([Claim 1]).
Furthermore, Patent Document 2 discloses “a rubber composition for a tire rim cushion or rubber finishing comprising from 55 to 75 parts by mass of a carbon black (1) having a nitrogen adsorption specific surface area of not less than 35 m2/g and less than 50 m2/g and from 5 to 20 parts by mass of a carbon black (2) having a nitrogen adsorption specific surface area of not less than 50 m2/g and not greater than 95 m2/g, per 100 parts by mass of a rubber component containing from 30 to 70 mass % of butadiene rubber having a cis-1,4 bond content of not less than 97% and a Mooney viscosity (ML1+4) of not less than 45 at 100° C., (T-cp)/(ML1+4), which is a ratio of (T-cp) [cps], a viscosity of a 5 mass % toluene solution at 25° C., to the Mooney viscosity, being at least 2.0, and from 30 to 70 mass % of other diene rubbers; the total of the carbon blacks (1) and (2) being from 60 to 95 parts by mass”.